The commonly followed definition of dementia is the one described by the International Statistical Classification of Diseases, 10th Revision (ICD-10, World Health Organization) or the Diagnostic and Statistical Manual of Mental Disorders (DSM-V, American Psychiatric Association). The most important aspect in the diagnosis of dementia is the assessment of overall mental and functions, including living environment, activities of daily living, cognition, mental status, and behavior. Physicians should diagnose dementia on the basis of not only cognitive test results or radiological findings but also other available information, including that obtained from the families or caregivers. Tests for the quantitative evaluation of cognitive function and dementia include the Mini-Mental State Examination (MMSE), Hasegawa Dementia Scale Revised (HDS-R), Clinical Dementia Rating (CDR), and Wechsler Memory Scale-Revised (WMS-R).